The telecommunications industry has always put an emphasis on the miniaturization of electronic circuits and components. As far as portable and handheld communicating devices are concerned this effort focuses particularly on the antenna which is usually one of the more cumbersome parts of a radio system. Because the trend is also in the reduction of the form factor of these devices the chief difficulty is to maintain antenna performances while they must fit in packages that are becoming increasingly smaller and slimmer. Moreover, all these communicating devices are often bound to embed multiple antennas adapted to the various types of wireless technologies supported which contributes to make their embedding even more difficult to achieve.
Indeed, it is not now infrequent that a cellular phone, e.g.: a GSM mobile phone (Global System for Mobile communications) also embeds a Bluetooth™ short range wireless link to connect the phone to another device; typically, to connect to a personal computer or to a mobile headset. Also, recent high-end mobile phones often include a GPS (Global Positioning System) receiver. And, most of the mobile computers and PDAs (Personal Digital Assistants) are equipped to allow connection to a wireless LAN (Local Area Network), e.g.: a Wi-Fi™ LAN so as to get access to the Internet within buildings and any public areas providing the appropriate wireless access points. Hence, those communicating devices must be equipped of one or more antennas each devised to efficiently operate at a particular wavelength typically in a frequency range as low as 850 MHz (106 Hertz) for the GSM to 5 GHz (109 Hertz), i.e., at wavelengths (λ) ranging respectively from about λ=35 cm (centimeter=10−2 meter) to λ=6 cm.
The standard way of implementing such an antenna is to draw it under the form of metallic traces on the same printed circuit board (PCB) that holds and links the components of any communicating device. An antenna structure commonly in use for that purpose is called IFA for “inverted F antenna” in reference to its overall shape 110, as shown in FIG. 1, where there is an open end and a grounded end with an intermediate feeding leg. IFA has become popular because it is a quarter wavelength (λ/4) antenna (thus, contributing to reduce the size occupied accordingly) and because it can conveniently be drawn on a single plane of a PCB. Hence, the name sometime also used of PIFA which stands for “planar inverted F antenna”. In this example of an antenna devised to operate at 2.45 GHz, in the middle of the frequency range mentioned above, i.e., at a wavelength of about 12 cm, the overall size occupied by the antenna in this example is just a rectangle of 8 mm by 6 mm (millimeter=10−3 meter). Indeed, a significant reduction of the overall dimensions is obtained by folding the antenna as shown 115. Folding, a standard technique, allows a reduction in the order of one-tenth of the wavelength (λ/10) as illustrated.
Nevertheless, the trend in the evolution of telecommunication components and devices is a constant reduction of their sizes while antennas must still abide by the rules of physics which require that their dimensions remain a finite fraction (¼ for an IFA like antenna) of the wavelength over which they must transmit and receive signals independently of any packaging constraints. A simple scaling of antenna dimensions to fit into a tighter package would indeed seriously impair their performances. This would be very detrimental to the quality and transmission range capability of the communicating device.
More particularly the invention intends to miniaturize systems of the antenna in package type which is a recent technology separate from conventional antenna-on-PCB solutions.
It is thus an object of the present invention to describe a technique that allows a further reduction of the overall space occupied by an antenna without sacrificing any of its electrical and transmission performances.
Further objects, features and advantages of the present invention will become apparent to the ones skilled in the art upon examination of the following description in reference to the accompanying drawings. It is intended that any additional advantages be incorporated herein.